An organic light-emitting diode (OLED) display device, which is also known as an organic electroluminescent display device, has many advantages. For example, the OLED display device is self-luminous, can be driven at a low voltage. Moreover, the OLED display device has high luminous efficiency, short response time, high definition and contrast, a wide viewing angle, and a wide working temperature range. Besides, flexible display and large-area full-color display can be achieved. Therefore, the OLED display device is regarded as a display device which has greatest development potential in the industry.
In the prior art, an OLED display panel generally comprises an anode, an organic functional layer and a cathode which are formed on a substrate sequentially. The organic functional layer generally comprises a hole injection layer arranged on the anode, a hole transport layer arranged on the hole injection layer, a light-emitting layer arranged on the hole transport layer, an electron transport layer arranged on the light-emitting layer, and an electron injection layer arranged on the electron transport layer. A light-emitting principle of the OLED display panel is that a semi-conductive material and an organic light-emitting material, driven by an electric field, emit light by means of carrier injection and recombination. Specifically, driven by a certain voltage, electrons and holes are injected into the electron injection layer and the hole injection layer from the cathode and the anode respectively, and the electrons and holes are transferred to the light-emitting layer through the electron transport layer and the hole transport layer respectively. The electrons and holes meet in the light-emitting layer and form excitons which excite luminescent molecules, and the luminescent molecules emit visible light after radiative relaxation.
A traditionally used manner for manufacturing metal layer films of the organic functional layer and the cathode in the OLED display panel is vacuum vapor deposition. With the development of technology, ink-jet printing, which has advantages compared with the vacuum vapor deposition, is gradually used by manufacturers.
In a process for manufacturing the OLED display panel, ink-jet printing has advantages, compared with the vacuum vapor deposition, in material utilization rate and cost. FIG. 1 schematically shows a conventionally used pixel design manner in which sub-pixel units of RGB colors are arranged side by side. Since definition of a display panel is improved continuously, more and more pixel units are arranged, while sizes of the pixel units become smaller and smaller. Therefore, an area for ink-jet operation of an ink-jet printer within a pixel unit is relatively small. The precision of an existing ink-jet printer cannot meet requirements for manufacture of the display panel gradually, and requirements for manufacture of a higher-definition display product cannot be met by the ink-jet printer due to its limitations. In order to overcome such a technical problem, a new two-in-one pixel design as shown in 2a is provided, which can effectively increase the area for ink-jet operation of the ink-jet printer. Therefore, requirements for manufacture of a higher-definition display product can be met. FIG. 2b schematically shows a magnified structure of a single sub-pixel structure of FIG. 2a, and FIG. 2c is a sectional view of FIG. 2b in A-A direction. In order to clearly explain technical problems existing in the prior art, FIG. 2b and FIG. 2c only schematically show a substrate, an anode, a dielectric layer, a pixel range defining structure and an organic functional layer. Structures of other parts are not schematically shown, but those skilled in the art can make specific arrangements according to needs. As shown in FIG. 2b and FIG. 2c, two adjacent sub-pixel structures having a same color are arranged together in such a two-in-one pixel process. On a substrate 1, anodes 2 of two adjacent sub-pixel structures having a same color are separated by a dielectric layer 3 arranged therebetween. A pixel range defining structure 4 is arranged on the anodes 2, and is used to define an ink-jet area. In an ink-jet process, functional material ink is instilled into the ink-jet area defined by the pixel range defining structure 4 by means of a plurality of nozzles of an ink-jet printer, and then a desired film 5 is obtained by drying. Technical problems exist in such a process. After anodes 2 are formed on the substrate 1, the anode need to be etched so as to form the dielectric layer 3. Therefore, the process is complicated. Moreover, since hydrophilicity and hydrophobicity of the dielectric layer 3 to the functional material ink are different from those of the pixel range defining structure 4 to the functional material ink, a non-uniform thickness of a film formed by the functional material ink in the ink-jet area can be caused easily.